JP2002075333A - Polymer secondary battery and method of manufacturing electrode for battery - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a polymer secondary battery having a high capacity, an excellent cycle characteristic and a low battery cell impedance. SOLUTION: In a method of manufacturing an electrode for battery, after forming a film of electrode material containing conduction auxiliary material and electrochemically active polymer as active material, the electrode material is heat-treated at a temperature lower than the carbonization temperature of the polymer.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a polymer secondary battery and a method for producing an electrode for a battery.

[0002]

2. Description of the Related Art Conventionally, an electric double layer capacitor has been used as a load fluctuation absorbing power supply device for the purpose of absorbing a pulse load of an electronic device typified by a cellular phone or regenerating energy of an electric vehicle or a fuel cell vehicle. I have.
However, the electric double layer capacitor has excellent power density and cycle life, but has a low energy density of about 1/100 of that of the secondary battery. In addition, with the recent development of portable devices, etc., the load current has been increasing due to the higher performance of CPUs and the cordless use of communication devices such as wireless LANs. It is becoming difficult to absorb.

Therefore, various electrochemical capacitors having a capacity ten times that of the electric double layer capacitor have been proposed. Above all, research on devices using electrochemically active polymers as electrode materials has been actively conducted.

As a device using a conductive polymer, there is a coin-type polyaniline lithium secondary battery already commercialized by Bridgestone and Seiko Electronic Components. This battery is characterized by high electromotive force of 3 V and low self-discharge. However, since the discharge current was as small as 10 μA, it was used only as a backup power supply for the memory. This is because the impedance of the battery cell is high.

In general, methods for lowering the impedance include increasing the amount of a conductive auxiliary material, reducing the amount of a binder, providing a buffer layer between a current collector and an electrode,
There is a method in which the current collector and the electrode are pressed and pressed. The method (1) has a drawback that the battery capacity is reduced because the amount of active material contained in the electrode is reduced. In the method (1), the shape of the electrode cannot be maintained, so that the electrode is missing and the cycle characteristics are deteriorated. In the methods and
Although effective for reducing the contact resistance between the current collector and the electrode, the resistance of the electrode itself cannot be reduced.

On the other hand, JP-A-8-315825 describes that a material having a polyacene skeleton structure, which is a heat-treated product of an aromatic condensation polymer comprising carbon, hydrogen and oxygen, is used for a battery electrode. . In addition, Japanese Unexamined Patent Publication No.
No. 163033 discloses that an organic polymer compound is heat-treated in a reducing atmosphere at a temperature lower than the carbonization end temperature, or in the air until significant oxidation starts, and then in a reducing atmosphere, a neutral atmosphere, Alternatively, there is described a method for producing an electrode material for a secondary battery, which comprises performing a heat treatment at a temperature lower than a carbonization end temperature in an oxidizing gas atmosphere. However, in the electrode materials described in these publications, a binder (binder) must be used at the time of forming an electrode. Therefore, the binder adheres between the electrode materials to increase the contact resistance. There is a problem that the resistance of the obtained electrode itself is high.

[0007]

SUMMARY OF THE INVENTION Therefore, an object of the present invention is to solve the above-mentioned problems, and to provide a large capacity,
An object of the present invention is to provide a polymer secondary battery having excellent cycle characteristics and low battery cell impedance.

[0008]

According to the present invention, an electrode material containing a conductive auxiliary material and an electrochemically active polymer as an active material is formed and then heat-treated at a temperature lower than the carbonization temperature of the polymer. And a method for producing a battery electrode.

The present invention also relates to a method for producing an electrode for a battery according to the above invention, wherein the electrode material does not contain a binder.

According to the present invention, there is provided a polymer secondary battery in which electrodes are opposed to each other via a separator or an electrolyte impregnated with an electrolytic solution, characterized by having the electrodes manufactured by the method of the present invention. Polymer secondary battery.

[0011] The present invention also relates to the polymer secondary battery of the above invention, wherein the above-mentioned electrode does not contain a binder.

[0012]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, a preferred embodiment of the present invention will be described.

As shown in FIG. 1, the polymer secondary battery according to the present embodiment comprises a negative electrode 4 formed of a polymer negative electrode active material and a conductive auxiliary material and formed on a current collector 5, and a polymer positive electrode active material. A positive electrode 2 made of a conductive auxiliary material and formed on a current collector 1 is opposed to each other with a separator impregnated with an electrolyte or an electrolyte 3 interposed therebetween.

In place of the above-mentioned negative electrode composed of a polymer negative electrode active material and a conductive auxiliary material, an electrode made of a known conductive metal may be used.

The electrode composed of the active material and the conductive auxiliary material is
After forming the electrode material containing the electrode active material and the conductive auxiliary material, the film is formed in the air, in an inert (neutral) atmosphere, in a reducing atmosphere,
Alternatively, it has been heat-treated in a vacuum atmosphere.

The doping of the electrode composed of the active material and the conductive auxiliary material can be performed by a known method. The above-mentioned electrode or electrode material may contain a known binder as long as it does not corrode by the electrolytic solution within a range that does not greatly reduce the resistance of the electrode itself.

The heat treatment at the time of preparing the electrode can be performed in the air, in an inert (neutral) atmosphere, in a reducing atmosphere, or in a vacuum atmosphere. As an inert (neutral) atmosphere,
An inert gas atmosphere such as argon, nitrogen, and helium may be used. Examples of the reducing atmosphere include a reducing gas atmosphere such as a hydrogen gas, an ammonia gas, and an ammonia-hydrogen mixed gas. As a vacuum atmosphere, 10 ⁻⁶ Torr (1.
33322 × 10 ⁻⁴ Pa) to 10 Torr (1.33322)
Preferably a reduced pressure atmosphere of ^{× 10 3 Pa), 10 -5} Torr
(1.33322 × 10 ⁻³ Pa) to 10 ⁻² Torr (1.3
A reduced pressure atmosphere of 3322 Pa) is more preferable. In these heat treatment atmospheres, it is preferable to perform heat treatment while aerating the gas in the apparatus so that the thermal decomposition product is discharged out of the heat treatment apparatus. Regarding the vacuum atmosphere, it is preferable to perform the heat treatment while continuing the suction operation by the pump.

The heat treatment temperature at the time of preparing the electrode is appropriately set according to the polymer active material used, and is a temperature higher than the melting or softening of the polymer active material.
It is necessary to perform heat treatment at a temperature lower than the carbonization temperature of the polymer active material. Here, the carbonization temperature is a temperature lower than the decomposition temperature of the electrochemically active polymer used as the active material or a temperature at which the activity as the electrode active material does not significantly decrease. When a binder is used, the temperature is preferably equal to or higher than the decomposition temperature of the binder used so that the non-conductive binder can be removed. The specific heat treatment temperature is appropriately set according to the above, but is 200 ° C. or more, or 400 ° C.
The above can be set, and within the range lower than the carbonization temperature of the polymer active material, 600 ° C. or less or 500 ° C.
You can set:

The heat treatment time is appropriately set according to the heat treatment temperature and the polymer active material used within a range in which desired characteristics are obtained and the polymer active material is not carbonized or its activity is not significantly reduced. One hour or more, and can be set within a range of one hour to 12 hours or 3 hours or less.

As the polymer material (polymer active material) used for the electrode active material, an electrochemically active polymer such as a conductive polymer is used. Polythienylene, polyisothianaphthene, polyaminoanthraquinone and their derivatives, polypyrrole, polymers of nitrogen-containing heterocyclic compounds such as polyindole, polypyridinediyl, polyquinoxaline, polypyridine, polymers of nitrogen-containing aromatic compounds such as polypyrimidine, Polymers of aromatic compounds such as polyparaphenylene and polyphenylenevinylene are exemplified.

Examples of the dopant and the electrolytic solution include an aqueous acid solution such as an aqueous sulfuric acid solution, an aqueous alkaline solution such as an aqueous potassium hydroxide solution, and a solution obtained by dissolving an electrolyte in an organic solvent.

As a separator impregnated with an electrolytic solution,
Known materials such as a porous film such as polyethylene and Teflon (registered trademark) can be used.

As the electrolyte interposed between the electrodes, a solid electrolyte, a gel electrolyte, and a molten salt can be used. Here, the solid electrolyte refers to an electrolyte containing no solvent molecules, and the gel electrolyte refers to an electrolyte containing a solvent obtained by plasticizing the solid electrolyte with an electrolyte (solvent). In addition, the electrolytic solution is a solution in which an electrolyte having no electron conductivity and having ion conductivity is dissolved in a solvent (water, organic solvent). A molten salt is an ion-conductive substance that is formed by heating and dissolving a solid salt or oxide at room temperature to form a liquid.

A conventional electrode composed of a polymer active material, a conductive auxiliary material and a binder has the following problems.

Since the binder is used at the time of forming the electrode, the contact resistance between the polymer active material and the conductive auxiliary material is high,
The conductivity of the electrode itself is low.

The capacity is reduced by the inclusion of impurities or low molecular weight polymers of active material polymers contained in the electrodes.

Since the porosity of the electrode is low, the impregnation amount of the electrolyte is small and the capacity is reduced.

When a large amount of the binder is added, the conductivity of the electrode itself is reduced. Therefore, since the minimum amount of the binder that can maintain the shape of the electrode is used, the strength of the electrode is weak.
The electrodes are easily dropped due to the expansion and contraction of the active material during charge and discharge, and as a result, the cyclability is reduced.

According to the present invention using the heat-treated electrode, the above problems 1 to 5 can be solved, and a polymer secondary battery having excellent characteristics can be provided.
This is considered to be due to the following reasons.

The problem is that the contact between the polymer active material and the conductive auxiliary material is point contact as shown in FIG. 3 when no heat treatment is performed, but the heat treatment causes the polymer active material to partially melt or soften. As shown in FIG. 2, the conductive material is brought into surface contact with the conductive auxiliary material, and the conductivity of the electrode itself increases due to an increase in the contact area. In addition, since the binder can be carbonized or removed by the heat treatment, the contact resistance between the polymer active material and the conductive auxiliary material can be reduced.

The problem is that the heat treatment can carbonize or remove impurities and low molecular weight substances of the polymer active material, so that the trapping of charges by these impurities or the deactivation of the charged polymer active material can be suppressed. Is improved.

The problem is that the porosity of the electrode is increased by the space (voids) formed by the impurities being removed by the heat treatment or by the shrinkage of the polymer active material by the heat treatment, and the impregnation amount of the electrolyte is increased. As the impregnation amount of the electrolytic solution increases, the contact area (reaction area) between the polymer active material and the electrolytic solution also increases, and the capacity increases.

The problem is that the heat treatment causes the contact between the polymer active material and the conductive auxiliary material to be in planar contact, and the contact area is increased, so that the strength of the electrode is increased, and the expansion and contraction of the polymer active material during charging and discharging is caused. The lack of the electrode can be suppressed, and the cyclability can be improved.

[0034]

The present invention will be described below in more detail with reference to examples.

Example 1 A positive electrode was prepared as follows. Using polyindole represented by the following formula as an active material,

[0036]

Embedded image

Gas-phase grown carbon is used as a conductive auxiliary material, and a mixture thereof (active material: conductive auxiliary material = 4: 1)
(Mass ratio)), 8% by mass of polyvinylidene fluoride (average molecular weight: 1100) as a binder resin (binder).
Was added. This slurry mixture was sufficiently stirred with a homogenizer, and a film was formed on a current collector sheet using a doctor blade. After film formation, 1 at 100-150 ° C
Vacuum dried for hours. After drying, the thickness of the electrode was reduced to 100 μm by pressing with a roll press. Then, it was cut into a predetermined shape to obtain a positive electrode.

The negative electrode 4 was prepared as follows. Using polyphenylquinoxaline represented by the following formula as an active material,

[0039]

Embedded image

Vapor-grown carbon is used as a conductive auxiliary material, and a mixture thereof (active material: conductive auxiliary material = 3: 1)
(Mass ratio)), polyvinylidene fluoride (average molecular weight: 1100) was added as a binder resin so as to be 8% by mass. This slurry-like mixture was sufficiently stirred with a homogenizer, and a film was formed on a Lumirror sheet using a doctor blade. After the film formation, it was vacuum-dried at 100 to 150 ° C. for 1 hour. After drying, the electrode cut into a predetermined shape was placed in a muffle furnace, heated to 500 ° C. for 1 hour, and held for 3 hours to obtain a negative electrode.

The positive electrode and the negative electrode, which are electrochemically or chemically doped using a sulfuric acid aqueous solution,
A secondary battery having the configuration shown in FIG. 1 was obtained by opposing the battery with the separator impregnated with the electrolytic solution interposed therebetween.

For the completed secondary battery, 1 to 10 mA
/ Cm ² constant current charging (1 to 10 C) up to 1.2 V and 1 to 10 mA / cm ² constant current discharging (1 to 10 C)
Was done. The theoretical capacity at this time was 264 Wh / kg (per mass of the negative electrode active material). As a result, the cell impedance was as low as 10 mΩ, the obtained capacity was 185 Wh / kg per mass of the negative electrode active material without depending on the discharge rate, and the capacity appearance rate was as high as 70%. Regarding the cycle characteristics, the number of cycles until reaching 80% of the initial capacity was 50,000 times. As for the capacity storage characteristics, the capacity after 30 days at 25 ° C. was 80%, which was similar to that of a lithium ion battery or a nickel hydride battery. FIG. 8 shows a discharge curve (charge / discharge current: 1 mA / cm ² ), and FIG. 10 shows cycle characteristics. Table 1 shows the evaluation results.

(Example 2) The secondary battery of this example has a negative electrode obtained by performing heat treatment without adding a binder when preparing the negative electrode in Example 1. By not including a binder in the electrode, the effect of increasing the amount of active material in the electrode and increasing the battery capacity and the effect of preventing a decrease in electrode conductivity due to the binder remaining after the heat treatment can be obtained. it can.

Hereinafter, a method for manufacturing the battery of this embodiment will be described.

The positive electrode was manufactured in the same manner as in Example 1.
For the negative electrode, the same polyphenylquinoxaline as in Example 1 was used as the active material, and vapor-grown carbon was used as the conductive auxiliary material, and the mass ratio (active material: conductive auxiliary material) =
Mixed 3: 1. The mixture was sufficiently stirred with a high-speed blender, and an electrode was formed in a predetermined shape using a hot press. The obtained electrode was placed in a muffle furnace, heated to 500 ° C. for 1 hour, held for 3 hours, cooled, and used as a negative electrode.

FIG. 5 shows an SEM photograph of the produced electrode. It can be seen that the polymer active material melts compared to the electrode without heat treatment (FIG. 4), and the contact with the conductive auxiliary material changes from point contact to surface contact and the contact area increases. Also,
It can also be seen that the electrode surface is porous.

For the completed secondary battery, 1 to 10 mA
/ Cm ² constant current charging (1 to 10 C) up to 1.2 V and 1 to 10 mA / cm ² constant current discharging (1 to 10 C)
Was done. The theoretical capacity at this time was 264 Wh / kg (per mass of the negative electrode active material). As a result, the cell impedance was as low as 6 mΩ, and the obtained capacity was 198 Wh / kg per mass of the negative electrode active material without depending on the discharge rate.
The capacity appearance ratio was as high as 75%. Regarding the cycle characteristics, the number of cycles until reaching 80% of the initial capacity was 70,000. In addition, the capacity storage characteristics are 2
After 30 days at 5 ° C., the capacity was 80%, showing characteristics similar to those of a lithium ion battery or a nickel hydrogen battery. In FIG.
FIG. 1 shows a discharge curve (charge / discharge current: 1 mA / cm ² ).
0 indicates the cycle characteristics. Table 1 shows the evaluation results.

Embodiment 3 The secondary battery of this embodiment has a negative electrode obtained by performing the heat treatment for preparing the negative electrode in Example 2 in an inert (neutral) atmosphere.
By performing the heat treatment in an inert (neutral) atmosphere, the oxidative deterioration of the polymer active material is suppressed, and the capacity can be improved.

The manufacture of the secondary battery of this example was performed in the same manner as in Example 2 except that the heat treatment was performed in an argon gas atmosphere in a muffle furnace in the preparation of the negative electrode.

FIG. 6 shows an SEM photograph of the produced electrode. It can be seen that the melting of the polymer active material and the porosity of the electrode surface are progressing as compared with the electrode that was heat-treated in the atmosphere (Example 2, FIG. 5).

For the completed secondary battery, 1 to 10 mA
/ Cm ² constant current charging (1 to 10 C) up to 1.2 V and 1 to 10 mA / cm ² constant current discharging (1 to 10 C)
Was done. The theoretical capacity at this time was 264 Wh / kg (per mass of the negative electrode active material). As a result, the cell impedance was as low as 4 mΩ, and the obtained capacity was 210 Wh / kg per mass of the negative electrode active material without depending on the discharge rate.
The capacity appearance ratio was as high as 80%. In the cycle characteristics as well, the number of cycles required to reach 80% of the initial capacity was 100,000. In addition, the capacity storage characteristics
After 30 days at 25 ° C., the capacity was 80%, showing characteristics similar to those of lithium ion batteries and nickel hydrogen batteries. FIG.
Shows a discharge curve (charge / discharge current: 1 mA / cm ² ),
FIG. 10 shows the cycle characteristics. Table 1 shows the evaluation results.

Example 4 The secondary battery of this example has a negative electrode obtained by performing the heat treatment in the preparation of the negative electrode in Example 2 in a vacuum atmosphere. By performing the heat treatment in a vacuum atmosphere, impurities in the electrode can be efficiently removed, the deactivation of the polymer active material can be suppressed, and the capacity can be improved.

The production of the battery of this example was performed in the same manner as in Example 2 except that in the preparation of the negative electrode, the temperature was raised to 400 ° C. for 1 hour in a vacuum furnace, and the heat treatment was performed for 1 hour. went.

FIG. 7 shows an SEM photograph of the produced electrode.
Electrode heat-treated in air or argon atmosphere (Example 2
It can be seen that the adhesion between the polymer active material and the conductive auxiliary material is further improved as compared with (FIG. 5) and Example 3 (FIG. 6).

For the completed secondary battery, 1 to 10 mA
/ Cm ² constant current charging (1 to 10 C) up to 1.2 V and 1 to 10 mA / cm ² constant current discharging (1 to 10 C)
Was done. The theoretical capacity at this time was 264 Wh / kg (per mass of the negative electrode active material). As a result, the cell impedance was as low as 1 mΩ, and the obtained capacity was 237 Wh / kg per mass of the negative electrode active material regardless of the discharge rate.
The capacity appearance ratio was as high as 90%. Regarding the cycle characteristics, the number of cycles required to reach 80% of the initial capacity was 500,000. In addition, the capacity storage characteristics
After 30 days at 25 ° C., the capacity was 80%, showing characteristics similar to those of lithium ion batteries and nickel hydrogen batteries. FIG.
Shows a discharge curve (charge / discharge current: 1 mA / cm ² ),
FIG. 10 shows the cycle characteristics. Table 1 shows the evaluation results.

(Example 5) The secondary battery of this example was obtained by performing a heat treatment (in air) using polyphenylquinoxaline represented by the above formula as an active material as a positive electrode (Example 2).
The electrode has the same structure as that of the negative electrode, a lithium foil is used as the negative electrode, and an organic solvent is used for the electrolytic solution. By using an organic solvent for the electrolyte, the electromotive force can be increased and the energy density can be increased.

Hereinafter, the manufacturing method of this embodiment will be described.

The positive electrode was manufactured in the same manner as the negative electrode of Example 2. The negative electrode used a lithium foil.

A PC / EC (propylene carbonate / ethylene carbonate) solution of LiPF ₆ was used as an electrolyte, and a positive electrode and a negative electrode were opposed to each other via a separator impregnated with the electrolyte to obtain a secondary battery. .

For the completed secondary battery, 1 to 10 mA
/ Cm ² constant current charging (1 to 10 C) up to 3.0 V and 1 to 10 mA / cm ² constant current discharging (1 to 10 C)
Was done. The theoretical capacity at this time was 660 Wh / kg (per mass of the negative electrode active material). As a result, the cell impedance was as low as 20 mΩ, the obtained capacity was 462 Wh / kg per mass of the negative electrode active material without depending on the discharge rate, and the capacity appearance rate was as high as 70%. Regarding the cycle characteristics, the number of cycles until reaching 80% of the initial capacity was 30,000 times. As for the capacity storage characteristics, the capacity after 30 days at 25 ° C. was 80%, which was similar to that of a lithium ion battery or a nickel hydride battery. FIG. 9 shows a discharge curve (charge / discharge current: 1 mA / cm ² ), and FIG. 11 shows cycle characteristics. Table 1 shows the evaluation results.

(Example 6) The secondary battery of this example was obtained by performing a heat treatment (argon atmosphere) using polyphenylquinoxaline represented by the above formula as an active material as a positive electrode (similar to the negative electrode of Example 3). Electrode), a lithium foil as a negative electrode, and an organic solvent as an electrolytic solution. Increase the electromotive force by using an organic solvent for the electrolyte,
Energy density can be increased.

Hereinafter, the manufacturing method of this embodiment will be described.

The positive electrode was manufactured in the same manner as the negative electrode of Example 3. The negative electrode used a lithium foil.

Using a PC / EC solution of LiPF ₆ as an electrolytic solution, a positive electrode and a negative electrode were opposed to each other via a separator impregnated with the electrolytic solution to obtain a secondary battery.

For the completed secondary battery, 1 to 10 mA
/ Cm ² constant current charging (1 to 10 C) up to 3.0 V and 1 to 10 mA / cm ² constant current discharging (1 to 10 C)
Was done. The theoretical capacity at this time was 660 Wh / kg (per mass of the negative electrode active material). As a result, the cell impedance was as low as 15 mΩ, the obtained capacity was 495 Wh / kg per mass of the negative electrode active material without depending on the discharge rate, and the capacity appearance rate was as high as 75%. Regarding the cycle characteristics, the number of cycles required to reach 80% of the initial capacity was 40,000. As for the capacity storage characteristics, the capacity after 30 days at 25 ° C. was 80%, which was similar to that of a lithium ion battery or a nickel hydride battery. FIG. 9 shows a discharge curve (charge / discharge current: 1 mA / cm ² ), and FIG. 11 shows cycle characteristics. Table 1 shows the evaluation results.

(Example 7) The secondary battery of this example was obtained by performing a heat treatment (vacuum atmosphere) using polyphenylquinoxaline represented by the above formula as an active material as a positive electrode (similar to the negative electrode of Example 4). Electrode), a lithium foil as a negative electrode, and an organic solvent as an electrolytic solution.
By using an organic solvent for the electrolyte, the electromotive force can be increased and the energy density can be increased.

Hereinafter, the manufacturing method of this embodiment will be described.

The positive electrode was manufactured in the same manner as the negative electrode of Example 4. The negative electrode used a lithium foil.

Using a PC / EC solution of LiPF ₆ as an electrolytic solution, a positive electrode and a negative electrode were opposed to each other via a separator impregnated with the electrolytic solution to obtain a secondary battery.

Regarding the completed secondary battery, 1 to 10 mA
/ Cm ² constant current charging (1 to 10 C) up to 3.0 V and 1 to 10 mA / cm ² constant current discharging (1 to 10 C)
Was done. The theoretical capacity at this time was 660 Wh / kg (per mass of the negative electrode active material). As a result, the cell impedance was as low as 10 mΩ, the obtained capacity was 561 Wh / kg per mass of the negative electrode active material without depending on the discharge rate, and the capacity appearance rate was as high as 85%. Regarding the cycle characteristics, the number of cycles until reaching 80% of the initial capacity was 70,000. As for the capacity storage characteristics, the capacity after 30 days at 25 ° C. was 80%, which was similar to that of a lithium ion battery or a nickel hydride battery. FIG. 9 shows a discharge curve (charge / discharge current: 1 mA / cm ² ), and FIG. 11 shows cycle characteristics. Table 1 shows the evaluation results.

(Comparative Example 1) A secondary battery was fabricated in the same manner as in Example 1 except that no heat treatment was performed during the preparation of the electrode.

For the obtained secondary battery, 1 to 10 mA
/ Cm ² constant current charging (1 to 10 C) up to 1.2 V and 1 to 10 mA / cm ² constant current discharging (1 to 10 C)
Was done. The theoretical capacity at this time was 264 Wh / kg (per mass of the negative electrode active material). As a result, the cell impedance was 30 mΩ. The capacity obtained by the 1C discharge was 170 Wh / kg per mass of the negative electrode active material, and the capacity appearance rate was 64%. Also, the capacity decreased as the discharge rate increased. Regarding the cycle characteristics, the number of cycles until reaching 80% of the initial capacity was 9000 times. The capacity preservation characteristic is that the capacity after 30 days at 25 ° C is 8
It was 0%, showing characteristics similar to those of lithium ion batteries and nickel hydrogen batteries. FIG. 8 shows a discharge curve (charge / discharge current: 1).
mA / cm ² ), and FIG. 10 shows the cycle characteristics.
Table 1 shows the evaluation results.

Comparative Example 2 A secondary battery was fabricated in the same manner as in Example 5, except that no heat treatment was performed during the preparation of the electrode.

For the obtained secondary battery, 1 to 10 mA
/ Cm ² constant current charging (1 to 10 C) up to 1.2 V and 1 to 10 mA / cm ² constant current discharging (1 to 10 C)
Was done. The theoretical capacity at this time was 660 Wh / kg (per mass of the negative electrode active material). As a result, the cell impedance was 70 mΩ. The capacity obtained by the 1C discharge was 400 Wh / kg per mass of the negative electrode active material, and the capacity appearance rate was 60%. Also, the capacity decreased as the discharge rate increased. Regarding the cycle characteristics, the number of cycles until reaching 80% of the initial capacity was 7000 times. The capacity storage characteristics are as follows.
It was 0%, showing characteristics similar to those of lithium ion batteries and nickel hydrogen batteries. FIG. 9 shows a discharge curve (charge / discharge current: 1).
mA / cm ² ), and FIG. 11 shows the cycle characteristics.
Table 1 shows the evaluation results.

[0075]

[Table 1]

[0076]

According to the present invention, the conductivity of the electrode can be greatly improved, and the impedance of the battery cell can be reduced. The reason is that the contact area between the polymer active material and the conductive auxiliary material increases due to the heat treatment during electrode preparation. In addition, since the strength of the electrode is improved by increasing the contact area between the polymer active material and the conductive auxiliary material, the electrode can be formed with a small amount or without using a non-conductive binder, This is because even when a binder is used, the binder, which is a non-conductive material, can be removed by heat treatment.

According to the present invention, the battery capacity can be increased. The reason for this is that the heat treatment during electrode preparation increases the amount of impregnation of the electrode with the electrolyte and increases the reaction area. In addition, the impurities are removed by the heat treatment, and the deactivation of the charged polymer active material can be suppressed.

Further, according to the present invention, the cyclability of the battery can be improved. The reason for this is that the contact area between the polymer active material and the conductive auxiliary material is increased, so that the strength of the electrode is improved, and the loss of the electrode due to expansion and contraction of the active material during charging and discharging can be suppressed.

[Brief description of the drawings]

FIG. 1 is a schematic sectional view of a battery according to an embodiment of the present invention.

FIG. 2 is a schematic diagram for explaining an electrode structure according to an example of the present invention.

FIG. 3 is a schematic diagram for explaining an electrode structure of a comparative example.

FIG. 4 is an SEM photograph (magnification: 50,000) of an electrode of a comparative example.

FIG. 5 is an SEM photograph (5000) of an electrode according to an example of the present invention.
0 times).

FIG. 6 is an SEM photograph (5000) of an electrode according to an example of the present invention.
0 times).

FIG. 7 is an SEM photograph (5000) of an electrode according to an example of the present invention.
0 times).

FIG. 8 is a graph showing discharge curves (charge / discharge current: 1 mA / cm ² ) of the batteries of the examples of the present invention and the comparative example.

FIG. 9 is a graph showing the discharge curves (charge / discharge current: 1 mA / cm ² ) of the batteries of the example of the present invention and the comparative example.

FIG. 10 is a graph showing the cycle characteristics of the batteries of the example of the present invention and the comparative example.

FIG. 11 is a graph showing the cycle characteristics of the batteries of the example of the present invention and the comparative example.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1, 5 Current collector 2 Positive electrode 3 Separator or electrolyte impregnated with electrolyte 4 Negative electrode 11 Current collector 12 Electrolyte 13 Electrode active material 14 Conductive auxiliary material

 ──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor Hiroyuki Shima Toru 5-7-1 Shiba, Minato-ku, Tokyo Inside NEC Corporation (72) Inventor Masato Kurosaki 5-7-1 Shiba, Minato-ku, Tokyo NEC Corporation (72) Inventor Yuji Nakagawa 5-7-1 Shiba, Minato-ku, Tokyo NEC Corporation (72) Katsuya Mitani 5-7-1 Shiba, Minato-ku, Tokyo NEC (72) Inventor Shinya Yoshida 5-7-1 Shiba, Minato-ku, Tokyo NEC Corporation (72) Inventor Tomoki Shinda 5-7-1 Shiba, Minato-ku, Tokyo NEC Corporation F-term in the formula company (reference) 5H029 AJ03 AJ05 AK16 AL16 AM03 AM07 AM16 CJ02 5H050 AA07 AA08 AA12 BA17 BA18 CA20 CA22 CA25 CB20 CB22 CB25 DA10 DA13 DA19 FA02 GA02 HA14

Claims (8)

[Claims] After forming an electrode material containing a conductive auxiliary material and an electrochemically active polymer as an active material,
A method for producing a battery electrode, wherein the heat treatment is performed at a temperature lower than the carbonization temperature of the polymer. 2. The method according to claim 1, wherein the heat treatment is performed in an inert atmosphere. 3. The method according to claim 1, wherein the heat treatment is performed in a vacuum atmosphere. 4. The method according to claim 1, wherein the heat treatment is performed in a reducing atmosphere. 5. The method for producing a battery electrode according to claim 1, wherein a binder is not contained in the electrode material. 6. The production method according to claim 1, wherein the electrode is used for a polymer secondary battery in which electrodes are arranged to face each other with a separator impregnated with an electrolyte or an electrolyte interposed therebetween. . 7. A polymer secondary battery in which electrodes are arranged to face each other with a separator impregnated with an electrolyte or an electrolyte interposed therebetween, comprising an electrode manufactured by the method according to claim 1. Polymer secondary battery. 8. The polymer secondary battery according to claim 7, wherein the electrode contains no binder.